Cilia and flagella are complex microtubular organelles that are ubiquitous among eukaryotes, including humans, where they are found in the respiratory tract, the female reproductive tract and on sperm cells. Ciliary and flagellar dysfunction resulting from the absence of outer arm dyneins has been reported to cause respiratory and fertility problems in humans and other mammals. The long term objectives of this work are to understand the mechanisms by which outer arm dyneins assemble into ciliary axonemes and to understand the role(s) of outer arm dyneins in ciliary motility by using a Tetrahymena thermophila mutant that is nonmotile and that lacks outer arm dyneins as a model system. Specifically, the role(s) that outer arm dyneins play in ciliary motility will be determined by a) testing the hypothesis that outer dynein arms are necessary for the formation of metachronal waves in ciliated cells by examining the ciliary structure of mutant cells with the scanning electron microscope and b) by determining the rate at which adjacent microtubule doublets slide relative to each other in cilia that lack outer arm dyneins. Cilia isolated from these mutants contain 22s dyneins (the dyneins that are thought to make up the outer arm) even though they lack outer arm dyneins. This suggests the hypothesis that Tetrahymena cilia contain two functionally distinct 22s dyneins, one that is located at the outer arm position and another that is bound elsewhere. That hypothesis will be tested by determining where 22s dyneins isolated from axonemes that lack outer dynein arms will bind when mixed with normal axonemes from which the dyneins have been removed chemically. Axonemes that do not have outer dynein arms contain 22s dyneins but lack one 85 kDa protein. This suggests that the missing protein mediates binding of 22s dynein to the outer arm position in normal axonemes. Thus, the gene that encodes the normal version of the putative outer arm attachment protein will be cloned in order to initiate analysis of that interesting protein. To clone the gene the protein will be isolated and sequenced, and the amino acid sequence will be used to design oligonucleotide probes. the probes will be used as primers in the polymerase chain reaction to amplify DNA encoding the outer arm attachment protein from cellular DNA. The amplified DNA will be cloned and sequenced to ensure the correct gene was cloned. Finally, extragenic revertants of the mutation will be generated and analyzed to identify other proteins that interact with the outer arm attachment protein in normal cilia.